Heatsink apparatus for de-coupling clamping forces on an integrated circuit package

ABSTRACT

A clamping system decouples the clamping forces in an electrical circuit assembly coupled to a heatsink. A heatsink clamping assembly applies controllable and predictable force on the electrical circuit assembly including an integrated circuit device (“chip”). The applied force is controlled to effectively ensure intimate contact between the chip and the heatsink to facilitate efficient chip cooling. The force applied to the chip is decoupled from the much higher force required to clamp the electrical interposer interconnect structure between the electrical circuit assembly and the printed circuit board.

RELATED APPLICATIONS

[0001] This application is a divisional of U.S. patent Ser. No.09/618,980, filed on Jul. 19, 2000, and which is hereby incorporated byreference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates generally to a system for attaching aheatsink to an integrated circuit device, and more particularly, to asystem for clamping a heatsink to an integrated circuit device thatapplies controllable force onto the integrated circuit device.

[0004] 2. Description of the Related Art

[0005] The use of integrated circuits is becoming more prevalent everyday. Integrated circuits (ICs) are used in a multitude of differentdevices from household appliances to computer applications. However, ICsare also rather fragile. They are generally thin pieces of silicon onwhich circuits are constructed. These IC “chips” are subject tocorrosion, environmental damage, physical shocks, and other damagemechanisms. For this reason, IC chips are packaged using a variety ofdifferent materials and package styles to protect them from possibledamage during transportation and use.

[0006] Conventional protective packaging is generally a plastic orceramic material used as a base for the IC chip and serving as a meansof expanding (“fanning out”) the electrical connections of the IC chip.The connections between the IC chip and the package are typicallyaccomplished using wire bonds or, in the case of “flip chip,” solderballs. In a “flip chip” arrangement, the top of the IC chip is flippedover face down onto the base package. Solder balls placed between theface of the chip and the base package provide electrical connectionsbetween the chip and the base package. Additionally, a lid may beattached over the IC to provide protection for the chip. The choice ofprotective packaging will be determined by various factors including theparameters of the chip itself, the IC application, and the packagingmaterial cost.

[0007] In addition to providing chip protection, a component is alsoneeded to allow the chip and package to make electrical connections toother devices. These connection components function as electricalcomponents, with circuits that connect the chip to the Printed CircuitBoard (PCB) or other device to which the chip is attached.

[0008] There are several different types of connection componentsallowing a chip and package to make electrical connections to a PCB. Theselection of the appropriate electrical connection component will dependto a large extent upon the particular design of the chip itself, thenumber of connections required, and the size of the package. Forexample, for connections with a chip encased in a protective packagethat is no larger than 32 mm square (1.59 in²) area, an array of solderballs (a ball grid array package or “BGA”) may be used to make theelectrical connections. Similarly, for packages no larger than 42 mmsquare (2.73 in²) area, an array of solder columns (a column grid arraypackage or “CGA”) may be used to make the electrical connections. Boththe ball and column grid arrays can be directly soldered to a PCB.

[0009] Both the ball and column grid array methods have a sizelimitation stemming from the long-term reliability of the connection.This limitation is mainly a function of the coefficient of thermalexpansion (CTE) mismatch that typically exists between the IC packageconstruction material and the PCB construction material. As a packagegets larger the outermost connections from the center of the package maybe stressed beyond their yield point as the IC chip heats the package.Therefore, for larger chips with a high lead count, or for more durablechip package systems, it is preferable to use an interposer component.An interposer provides an array of compressible contact points, suchpoints being comprised typically of a polymer with imbedded electricallyconductive metal or comprised of a metal spring structure. The requiredelectrical connection is accomplished through contact pressure ratherthan a rigid bond. By being a compliant connection the interposer thuseffectively decouples heat expansion stresses that can occur between thepackage and the PCB. However, when using an interposer to provide anelectrical connection between a packaged IC and a PCB, considerablepressure must be applied to ensure a good low resistive electricalcontact connection is achieved.

[0010] Certain IC chips also require the capability to dissipate a largeamount of heat energy. For example, some high-powered chips may give offover 100 watts of heat energy. For such high-powered chips, the coolingprovided by ambient air is not sufficient to prevent the chip fromoverheating. An additional component for removing the heat from the chipis required. A heatsink is commonly attached to an IC chip package, witha thermal interposer material in-between, in order to provide superiorheat dissipation. The thermal interposer provides good thermalconductivity between the device and heatsink. In a conventional system,the heatsink may be attached, with a thermal interposer materialin-between, to the package lid protecting the chip, or if no lid isused, directly to the chip itself.

[0011] The entire assembly consisting of the heatsink, the thermalinterposer, the chip, the base package, and the electrical connectioncomponents, is clamped together to ensure proper electrical connectionsand heat transfer capabilities. Significant clamping force (oftenexceeding several hundreds of pounds) is required to clamp thechip-package-interposer-PCB arrangement tightly enough to ensure aproper electrical connection through the interposer. Theheatsink-to-chip connection does not require a similar clamping force toprovide heat transfer capability. However, because the entire assemblyis clamped together when a conventional heat sink structure is used, allcomponents are subjected to the same clamping force. This clamping forcecould damage the chip itself, even though a lid may be used, since thelid could compress into the underlying chip.

[0012] In the conventional packaged chip and heatsink arrangement wherethe chip is covered by a lid, the heatsink and thermal interposer do notcontact the chip directly. Heat must pass through the air layer or otherconductive layer between the chip and the lid, as well as through thelid itself, and the thermal interposer, before being dissipated by theheatsink. Such an arrangement makes it difficult to effectively coolcertain high-powered chips. A preferable arrangement is to providecontact directly between the heatsink and the chip itself. Thisarrangement provides for superior heat transfer properties. However,without a lid present to absorb some of the compressive forces, extremecare must be taken to ensure that the chip is not crushed in thissituation due to the clamping force required for the rest of theassembly.

[0013] Thus a high-powered chip packaging assembly that includes both aheatsink and an electrical interposer has two different, competingclamping force needs. Significant clamping force is required forachieving proper connections in the chip-package-electricalinterposer-PCB portion of the assembly. However, significantly lessclamping force is desirable between the chip-thermal interposer-heatsinkassembly, to avoid damaging the chip. Thus, there is a need for a systemthat decouples the clamping forces between these two sections of theoverall assembly.

SUMMARY OF THE INVENTIONS

[0014] The present invention provides a system that decouples theclamping force in an electrical circuit assembly coupled to a heatsink.A heatsink clamping assembly applies controllable and predictable forceon the electrical circuit assembly including a packaged microelectronicintegrated circuit device (“chip”). The applied force is controlled toeffectively ensure intimate contact between the chip and the heatsink tofacilitate efficient chip cooling. The force applied to the chip isdecoupled from the much higher force required to clamp the interposerinterconnection between the electrical circuit assembly and the printedcircuit board. There are certain instances where the base of the heatsink may be a hollow chamber or heat pipe structure, and as such couldbe damaged if the full clamping force were required to be imposed.

[0015] In one embodiment, a heatsink clamping assembly comprises anelectrical circuit assembly electrically connected to a printed circuitboard (PCB). The electrical assembly includes an electrical circuit. Abacking plate coupled to studs contacts the PCB, and the studs extendthrough apertures in the PCB. A clamp plate with a window contacts theedges of the electrical assembly while allowing the electrical circuitto pass through the window. The studs pass through the clamp plate, anda first pair of clamp nut assemblies clamps the electrical circuitassembly and PCB between the backing plate and the clamp plate.

[0016] A heatsink contacts a thermal interposer on top of the electricalcircuit, and resides slightly above the clamp plate. The studs extendthrough the heatsink. A second pair of clamp nut assemblies connects theheatsink to the backing plate. The force used upon the first and secondpairs of clamp nut assemblies may differ, thereby decoupling the twoforces.

[0017] In one embodiment, the electrical circuit assembly comprises anelectrical circuit, a package electrically coupled to the electricalcircuit, and an electrical interposer electrically coupled to thepackage. The electrical interposer provides an electrical connection tothe PCB. In one embodiment, the electrical circuit is an integratedcircuit flip chip.

[0018] The features and advantages described in the specification arenot all-inclusive, and particularly, many additional features andadvantages will be apparent to one of ordinary skill in the art in viewof the drawings, specification, and claims hereof. Moreover, it shouldbe noted that the language used in the specification has beenprincipally selected for readability and instructional purposes, and maynot have been selected to delineate or circumscribe the inventivesubject matter, resort to the claims being necessary to determine suchinventive subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1A is an exploded three-dimensional view of the elements of aclamping assembly for an integrated circuit with a heatsink in anembodiment of the present invention.

[0020]FIG. 1B is an exploded three-dimensional view of the elements of aclamping assembly for an integrated circuit with a heatsink in anotherembodiment of the present invention.

[0021]FIG. 2 is a cut-away view of the layers of a clamping assembly foran integrated circuit with a heatsink in an embodiment of the presentinvention.

[0022]FIG. 3 is a top view of a heatsink and two vertical sliced viewsof the heatsink in an embodiment of the present invention.

[0023] The figures depict a preferred embodiment of the presentinvention for purposes of illustration only. One skilled in the art willreadily recognize from the following discussion that alternativeembodiments of the structures and methods illustrated herein may beemployed without departing from the principles of the inventiondescribed herein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Reference will now be made in detail to several embodiments ofthe present invention, examples of which are illustrated in theaccompanying drawings. Wherever practicable, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

[0025]FIG. 1A is an exploded view of the components in an embodiment ofa clamping assembly 100. Clamping assembly 100 includes an electricalcircuit assembly 111, a printed circuit board (“PCB”) 130, a backingplate 140, a clamp plate 150, a thermal interposer 114, and a heatsink160. Clamping assembly 100 has a first clamped group of components and asecond clamped group of components, wherein the first and second groupsmay be clamped together using different amounts of force.

[0026] The first clamped group of components includes the electricalcircuit assembly 111, the PCB 130, the backing plate 140 and the clampplate 150. Electrical assembly 111 includes an electrical circuit 110;however, no clamping force is applied to the electrical circuit 110within the first clamped group of components. Backing plate 140 isconnected to two studs 142A and 142B. PCB 130 includes two apertures133A and 133B, dimensioned to allow the studs 142 to pass through. Clampplate 150 includes two apertures 153A and 153B, dimensioned to allow thestuds 142 to pass through. Clamp plate 150 also includes a clamp platewindow 156, which runs through the clamp plate 150, and is dimensionedto fit around the electrical circuit 110 and prevent the electricalcircuit 110 from being subjected to the clamping force applied to thefirst clamped group of components. A pair of clamp nut assemblies 152Aand 152B clamp onto the studs 142 above the clamp plate 150, and may beadjusted to provide the first clamped group of components with thedesired clamping force.

[0027] The electrical circuit assembly 111 and the PCB 130 must be matedtogether tightly in order to assure a good electrical connection betweentheir components. Typically, a force of approximately 60-80 grams percontact (0.13-0.18 pounds per contact) is required to assure properelectrical contact. This translates into a stud 142 clamping force ofapproximately 90-120 kilograms force (190-260 pounds force). Because theelectrical circuit 110 passes through the clamp plate window 156, thisforce is not applied to the electrical circuit 110.

[0028] The second clamped group of components clamps the electricalcircuit 110 to the heatsink 160, with the thermal interposer 114in-between. The heatsink 160 includes two apertures 163A and 163B,dimensioned to allow the studs 142 to pass through. A pair of clamp nutassemblies 162A and 162B clamps onto the studs 142 above the heatsink160, and may be adjusted to provide the second clamped group ofcomponents with the desired clamping force.

[0029] The clamp plate 150 is dimensioned to approximately match thethickness of the electrical circuit 110. Thus, when the heatsink 160 isclamped on top of the clamp plate 150, the heatsink 160 contacts boththe clamp plate 150 and the electrical circuit 110, with the thermalinterposer 114 in-between, and provides a thermal conducting connectionfor removing heat from the electrical circuit 110. Maintaining a properthermal conducting connection requires significantly less clamping forcethan the electrical connection between the PCB 130 and the electricalcircuit assembly 111. A stud 142 clamping force of approximately 4.5-6.8kilograms force (10-15 pounds force) is applied to the second clampinggroup to provide a good thermal conduction connection between theheatsink 160 and the electrical circuit 110.

[0030] The backing plate 140 and the clamp plate 150 are composed of arigid material. In one embodiment, the backing plate 140 and the clampplate 150 are composed of steel. Heatsink 160 is composed of any highlythermally conductive material, for example, aluminum, copper, or evensome impregnated polymer material. In some cases, a combination ofmaterials are used, for example: aluminum for the heat sink finstructure and copper for a heat sink base or heat sink base heat pipe.The studs 142 and nut clamping assemblies 152 and 162 are composed of arigid material capable of carrying a significant clamping force. Thedimensions of the PCB 130, backing plate 140, clamp plate 150, thermalinterposer 114, and heatsink 160 are dependent upon the size of theelectrical circuit 110 and the electrical circuit assembly 111. The PCB130, backing plate 140, clamp plate 150 and heatsink 160 are alldimensioned to have a surface area large enough to accommodate aperturessurrounding the electrical circuit assembly 111 to allow the studs 142to pass through for clamping. The studs 142 are dimensioned to besufficiently long enough to pass through the PCB 130, electrical circuitassembly 111, clamp plate 150, thermal interposer 114, and heatsink 160and connect to the clamp nut assemblies 152 and 162.

[0031]FIG. 1B is an exploded view of the components in anotherembodiment of a clamping assembly 102. Clamping assembly 102 similarlycontains a first and a second clamped group of components as describedregarding clamping assembly 100. However, in clamping assembly 102, theelectrical circuit is an integrated circuit (“IC”) chip 110. Theelectrical circuit assembly 111 is a package 112 and an electricalinterposer 120. Clamping assembly 102 decouples the force applied to thefirst clamped group of components (package 112, electrical interposer120, PCB 130, backing plate 140, and clamp plate 150) from the forceapplied to the second clamped group of components (IC chip 110, chipthermal interposer 114, and heatsink 160).

[0032] Package 112 holds and protects the IC chip 110 and provideselectrical connections to the chip 110. The electrical interposer 120provides an electrical connection between the IC chip 110 connections(through the package 112) and the PCB 130. Clamping assembly 102 furtherincludes a chip thermal interposer 114, which provides a thermalconducting layer between the chip 110 and the heatsink 160.

[0033] Clamping assembly 102 is designed for the particular needs ofchips that have the following characteristics: (1) they are high-wattagechips, typically greater than 100 watts, and (2) they have highelectrical interconnect counts, requiring relatively large chips,typically 20 mm square (0.62 in²) in area or larger. High-wattage chipstypically generate too much heat to use a lidded package configuration,and it is preferable to attach a heatsink directly onto the back of thechip through a thermal interposer. Large chips require large packages,and as discussed previously, an electrical interposer 120 is moresuitable than ball or column grid arrays for providing larger IC chippackages with electrical connections to a PCB.

[0034] Thus IC chip 110 is typically a high-wattage chip emittingapproximately 100 watts or more, and is typically 20 mm square or largerin size. However, it will be evident to one of skill in the art that theclamping assembly of the present invention may be used with smaller ICchips of lower wattage. In order to further protect the IC chip 110, andimprove the heat transfer capabilities between the IC chip 110 and theheatsink 160, clamping assembly 102 includes the chip thermal interposer114. Chip thermal interposer 114 may be a layer of a conductive materialsuch as silicone grease or a thermal epoxy that coats the IC chip 110.

[0035] The IC chip 110 is attached to the package 112. The package 112may be one of a number of different types of IC chip packages. In oneembodiment, a “flip chip” type of IC chip 110 and package 112 is used.In a “flip chip,” the IC chip 110 is flipped over onto the package 112so that the bond pads on the top of the IC chip 110 are directly abovethe top of the package 112, which contains a footprint of the IC chip110 electrical connections. The bond pads between the IC chip 110 andpackage 112 have solder balls bonded to them that form physical andelectrical connections between the IC chip 110 leads and the package112.

[0036] In one embodiment, package 112 is composed of a ceramic material.In another embodiment, package 112 is composed of a plastic or laminatematerial. The size of the package 112 is determined by the size of theIC chip 110. Package 112 is dimensioned to be larger in area than the ICchip 110, allowing a portion of the package 112 to provide surfacecontact with the clamp plate 150 as the IC chip 110 passes through theclamp plate window 156. In one embodiment including an IC chip ofapproximately 20 mm square, the package size is approximately 45 mmsquare (3.14 in²) area or larger. It will be evident to one of skill inthe art that a smaller package may be used if a smaller IC chip is used.

[0037] The electrical interposer 120 provides an electrical connectionbetween the package 112 and the PCB 130. The electrical interposer 120consists of a sheet of carrier material that captures an array ofcompressible conductive buttons that have pieces of electricallyconductive material embedded within them to connect leads on the package112 to leads on the PCB 130. In one embodiment, the membrane material isa polyamide film. In another embodiment, a ceramic or polymer framecontains an array of spring-like structures typically made ofgold-plated or silver-plated beryllium, copper, molybdenum, or similarmetals. The electrical interposer 120 is sized to be as large orslightly larger than the package 112. Thus, for a package size ofapproximately 45 mm square, the electrical interposer size will beapproximately 50 mm square. The dimensions of the PCB 130, backing plate140, clamp plate 150 and heatsink 160 are dependent upon the size of theIC chip 110, the package 112, and the electrical interposer 120.

[0038] In one embodiment, the heatsink 160 includes a heat pipe thatthermodynamically connects to the IC chip 110 through the chip thermalinterposer 114. A heatsink 160 including a heat pipe typically providessuperior heat transfer properties compared to the heatsink alone. A heatpipe is a block of a conductive metal, such as copper, with a hollowcavity inside. The cavity is airtight and maintained at a partialvacuum, and contains a fluid selected for its boiling temperature. Wateris often selected for the fluid, as are various alcohols. Heatcontacting one side of the heat pipe vaporizes the water within thepartial vacuum, and the vapor transfers heat to the heat sink side ofthe heat pipe where it condenses. In this manner, heat is spread overthe base of the heat sink very efficiently, as the heat pipe wicks heataway from the IC chip 110 and transfers it to the heatsink 160.

[0039] A heat pipe is hollow and therefore somewhat fragile. However,because the clamping assembly 102 decouples the clamping force appliedto the heatsink 160 from the clamping force applied to the othercomponents, a low clamping force loading on the heat pipe may beachieved as necessary.

[0040]FIG. 2 is a cut-away view of the layers of another embodiment of aclamping assembly 104 for an electrical circuit with a heatsink. Theheatsink of clamping assembly 104 includes a heat pipe 200. The backingplate 140 and studs 142 are shown separated from the rest of theclamping assembly 104. When clamping assembly 104 is fully assembled,the backing plate 140 contacts the PCB 130 and forms the bottom layer ofthe clamping assembly 104.

[0041] Moving from the bottom to the top of the clamping assembly 104,the following components comprise a first group of clamped components:the backing plate 140 contacts the PCB 130; the PCB 130 contacts theelectrical interposer 120; and the electrical interposer 120 contactsthe package 112. The top surface of package 112 that is external to thechip also contacts the clamp plate 150. The package 112 is attached tothe IC chip 110; however, the IC chip 110 passes through the clamp platewindow and therefore does not contact the clamp plate 150. The IC chip110 is therefore not included in the first clamped group of components.

[0042] The studs 142 are connected to the backing plate 140 and passthrough apertures in the PCB 130 and clamp plate 150. The first group ofclamped components between the clamp plate 150 and the backing plate 140are clamped together through a first clamping assembly that connectsonto the pair of studs 142A and 142B. The first clamping assemblyconsists of a pair of clamping pressure transfer bushings 258A and 258B,a pair of clamp springs 256A and 256B, and a pair of clamp nuts 254A and254B.

[0043] Moving from the top of the first clamped group of components tothe top of the entire clamping assembly 104, the following componentscomprise a second group of clamped components: the IC chip 110 contactsthe chip thermal interposer 114 (for example, a thin layer of grease orsilicon); the chip thermal interposer 114 contacts a heat pipe 200; theheat pipe 200 contacts a bonding material layer 205; and the bondingmaterial layer 205 bonds the heat pipe 200 to a heatsink. The heatsinkincludes a heatsink bottom plate 266, a set of heatsink fins 264, and aheatsink top plate 262.

[0044] The studs 142 pass through apertures in the heat pipe 200, theheatsink bottom plate 266 and the heatsink top plate 262. The secondgroup of clamped components is clamped together through a secondclamping assembly that connects onto the pair of studs 142A and 142B.The second clamping assembly consists of a pair of inserts 270A and270B, a pair of spring washers 272A and 272B, and a pair of clamp nuts274A and 274B.

[0045]FIG. 3 is a top view of a heatsink that requires 4 studs. FIG. 3includes two different vertical sliced views through the heatsink, in anembodiment of the present invention. View 301 includes a heat pipe 200,a heatsink bottom plate 266, a set of heatsink fins 264, and a heatsinktop plate 262. View 302 is a vertical slice through the heatsink alongthe apertures 163A and 163B, illustrating the apertures 163 in theheatsink top plate 262, the heatsink bottom plate 266, and the heat pipe200 that allow the studs to pass through the heatsink. View 302 alsoillustrates that the heat sink top plate 262 includes a set of recessedcavities 263A and 263B around each aperture 163, allowing the heat sinkclamping assemblies to be recessed into the heatsink itself.

[0046] In FIG. 3, the heatsink is shown to include four apertures (163A,B, C and D) dimensioned to allow a set of four studs to pass through theheatsink for use in clamping together the clamping assembly. It will beevident to one of skill in the art that the clamping assembly may bedesigned to have different numbers of studs used for clamping Forexample, in one embodiment, there is a pair of two studs. In anotherembodiment, a set of four studs is used. The number of apertures throughthe heatsink, PCB and clamp plate component of the clamping assemblycorresponds to the number of studs used.

[0047] In one embodiment, the clamping assembly includes severaldifferent IC chips. In this embodiment, a single large heatsink removesheat from several different IC chips. The clamp plate contains severalwindows corresponding to the number of IC chips, or one large window toencompass all the chips, or any combination of windows between,dimensioned to allow an IC chip to pass through and contact the heatsinkdirectly. The clamping assembly components are dimensioned toaccommodate the area of several IC chips as well as the apertures usedto allow the studs to pass through the clamping assembly.

[0048] Although the invention has been described in considerable detailwith reference to certain embodiments, other embodiments are possible.As will be understood by those of skill in the art, the invention may beembodied in other specific forms without departing from the essentialcharacteristics thereof. For example, different types of electricalcircuit assemblies may be used within the invention. Additionally, aheat pipe may be included in the heatsink assembly. Accordingly, thepresent invention is intended to embrace all such alternatives,modifications and variations as fall within the spirit and scope of theappended claims and equivalents.

What is claimed is:
 1. A clamping system for electrical assemblysystems, comprising: an electrical circuit assembly having a firstsurface and a second surface; an electrical circuit mounted on the firstsurface of the electrical circuit assembly and electrically coupled tothe electrical circuit assembly; a first set of electrical contactsmounted on the second surface of the electrical circuit assembly andelectrically coupled to the electrical circuit assembly; a printedcircuit board including a second set of electrical contacts; a clampplate mounted on the first surface of the electrical circuit assemblydimensioned not to overlap with the electrical circuit; a first clampingassembly mechanically coupling the clamp plate to the printed circuitboard and configured to apply a first force onto the first surface ofthe electrical circuit assembly by compressing the electrical circuitassembly between the clamp plate and the printed circuit board, thefirst force contributing to an electrical coupling between the first setof electrical contacts and the second set of electrical contacts; aheatsink assembly mounted on the electrical circuit; and a secondclamping assembly mechanically coupling the heatsink assembly to theprinted circuit board and configured to apply a second force onto theelectrical circuit by compressing the electrical circuit between theheatsink assembly and the printed circuit board, the second forcecontributing to a thermodynamic coupling between the heatsink assemblyand the electrical circuit.
 2. The clamping system of claim 1, whereinthe clamp plate further includes a window.
 3. The clamping system ofclaim 2, wherein the window bounds four sides of the electrical circuit.4. The clamping system of claim 2, wherein the window bounds three sidesof the electrical circuit.
 5. The clamping system of claim 1, whereinthe heatsink assembly comprises: a heatsink bottom plate; and a thermalinterposer mounted between the heatsink bottom plate and the electricalcircuit.
 6. The clamping system of claim 5, wherein the thermalinterposer is a silicone grease.
 7. The clamping system of claim 1,wherein an electrical interposer is mounted on the second surface of theelectrical circuit assembly and electrically couples the first set andthe second set of electrical contacts.
 8. A clamping system fordecoupling clamping forces on an electrical circuit assembly comprising:an electrical circuit assembly including an electrical circuit; aprinted circuit board electrically coupled to the electrical circuitassembly; a clamp plate for applying a first predetermined force ontothe electrical circuit assembly, the clamp plate mounted on theelectrical circuit assembly and mechanically coupled to the printedcircuit board; and a heatsink thermally coupled to the electricalcircuit, the heatsink further mechanically coupled to the printedcircuit board and configured to apply a second predetermined force ontothe electrical circuit.
 9. The clamping system of claim 8, wherein thefirst predetermined force is of greater magnitude than the secondpredetermined force.
 10. The clamping system of claim 8, wherein theheatsink comprises a hollow chamber.
 11. The clamping system of claim 8,wherein the first predetermined force is a clamping force clamping theelectrical circuit assembly between the clamping plate and the printedcircuit board.
 12. A method for clamping electrical circuit assemblies,comprising the steps of: clamping with a first clamping assembly a firstgroup of components comprising a printed circuit board and an electricalcircuit assembly having an electrical circuit; and clamping with asecond clamping assembly a second group of components comprising theelectrical circuit, and a heatsink assembly, whereby clamping forcesclamping the first group of components are of different magnitude thanclamping forces clamping the second group of components.
 13. The methodof claim 12, wherein the second group of components also includes theprinted circuit board.
 14. The method of claim 13, wherein the secondgroup of components includes a thermal interposer.